Influences of the N- and C-termini of the distal nephron inward rectifier, ROMK

The inward rectifying potassium channels of the ROMK family are present in the distal nephron of the kidney. These channels have two membrane spanning portions, between which lies a hydrophobic domain thought to confer the majority of the conductive properties of the channel. The N- and C-termini are both intracellular. In this paper we have examined the contribution of the N- and C-termini to the pore by examining the interaction of Cs+ with the channels. ROMK1 has an additional 19 amino acids on its N-terminus in comparison to ROMK2. The C-terminus of ROMK2 was extended by addition of a streptavidin tag (sfROMK2). Currents were measured following expression in Xenopus oocytes using two-electrode voltage clamp. ROMK1, ROMK2 and sfROMK2 exhibited concentration- and voltage-dependent block of inward currents by extracellular Cs+. The Hill coefficients were not significantly different from one. The mean Kd values at 0 mV were 100.6 +/- 10.6, 63.1 +/- 3.9 and 40.6 +/- 9.4, respectively (p < 0.05). The electric distances (delta) were 0.94 +/- 0.06, 1.0 +/- 0.05 and 1.37 +/- 0.06 respectively. The delta of sfROMK2 was greater than either ROMK1 or ROMK2 (p < 0.001). ROMK1, ROMK2 and sfROMK2 are sensitive to extracellular Cs+. Block was both concentration- and voltage-dependent. sfROMK2 is most Cs+-sensitive. ROMK1 contains an additional N-terminal 19 amino acids. Thus the pore properties of these two isoforms are subtly different, and influenced by the N-terminus. The lower Kd in sfROMK2 suggests that the streptavidin tag, and perhaps the C-terminus, also affect the pore.

WMS-III performance in patients with temporal lobe epilepsy: group differences and individual classification

The utility of the WMS-III in detecting lateralized impairment was examined in a large sample of patients with temporal lobe epilepsy. Methods of analysis included evaluation of group means on the various indexes and subtest scores, the use of ROC curves, and an examination of Auditory-Visual Index discrepancy scores. In addition, performance on immediate and delayed indexes in the auditory and the visual modality was compared within each group. Of the WMS-III scores, the Auditory-Visual Delayed Index difference score appeared most sensitive to side of temporal dysfunction, although patient classification rates were not within an acceptable range to have clinical utility. The ability to predict laterality based on statistically significant index score differences was particularly weak for those with left temporal dysfunction. The use of unusually large discrepancies led to improved prediction, however, the rarity of such scores in this population limits their usefulness. Although the utility of the WMS-III in detecting laterality may be limited in preoperative cases, the WMS-III may still hold considerable promise as a measure of memory in documenting baseline performance and in detecting those that may be at risk following surgery.

A randomized controlled trial of a community-based consultation service to prevent falls

BACKGROUND

Multifaceted programs that combine assessment with interventions have been shown to reduce subsequent falls in some clinical trials. We tested this approach to see whether it would be effective if offered as a consultation service using existing health care resources.

METHODS

The subjects of this randomized controlled trial had to be aged 65 years or more and had to have fallen within the previous 3 months. They were randomly assigned to receive either usual care or the intervention, which consisted of in-home assessment in conjunction with the development of an individualized treatment plan, including an exercise program for those deemed likely to benefit. The primary outcomes were the proportion of participants who fell and the rate of falling during the following year. Visits to the emergency department and admissions to hospital were secondary outcomes.

RESULTS

One hundred and sixty-three subjects were randomly assigned to either the control or the intervention group, and 152 provided data about their falls. There were no significant differences between the control and intervention groups in the cumulative number of falls (311 v. 241, p = 0.34), having one or more falls (79.2% v. 72.0%, p = 0.30) or in the mean number of falls (4.0 v. 3.2, p = 0.43). Analysis of secondary outcomes (health care use) also showed no significant differences between the intervention group and the control group. In the Cox regression analysis, there was no significant difference between the groups in the proportion of subjects having one or more falls (p = 0.55), but there was a significantly (p < 0.001) longer time between falls in the intervention group. In a post hoc subgroup analysis, subjects with more than 2 falls in the 3 months preceding study entry who had been assigned to the intervention group were less likely to fall (p = 0.046) and had a significantly longer time between falls (p < 0.001), when compared with the group who received usual care.

INTERPRETATION

The intervention did not decrease significantly the cumulative number of falls, the likelihood of participants having at least one fall over the next year or the mean number of falls. It did increase significantly the time between falls in a survival analysis when age, sex and history of falling were used as covariates.

Biophysical effects of pore mutations of ROMK1

Potassium channels are ubiquitous, being present in all living organisms. These proteins share common structural elements, which confer common functional features. In general, all K+ channels have a high selectivity for K+, and are blocked by cations of similar dimensions, such as Cs+ and Ba2+. Mutations in the pore region tend to lead to either the total loss of function or K+ selectivity. We have made mutations to one of the most highly conserved residues of the pore, glycine-143, of the inward rectifier ROMK1 (Kir1.1), and examined the resulting channel properties in the Xenopus oocyte expression system with a two-electrode voltage clamp. Mutations G143A and G143R resulted in failure to express functional channels. Co-injection of wild-type ROMK1 cRNA with these mutants led to rescue of channel function, which was different from wild-type ROMK1. In both mutants, the sensitivity to Ba2+ and Cs+ was increased, the rate of onset of block by Ba2+ was enhanced, and the selectivity to potassium was reduced. Whereas the crystallographic evidence shows that cations bind to the carbonyl backbone of the pore-lining residues, the present results indicate that the side chains of these amino acids, which face away from the pore lining, also affect permeation.

Visual signal detection measured by event-related potentials

Signal Detection tasks typically involve within-subject signal changes. Such a procedure does not lend itself to event-related potential (ERP) experiments where the need for averaging necessitates the maintenance of consistent stimulus parameters. In the present ERP study we adopt a novel approach to thresholding that allows within-subject signal manipulation. The Signal Detection task required the identification of letter targets, formed from dots, in a random dot field. ERP waveforms were segmented into three windows corresponding to N1, N2, and P300 components. Analysis shows that ERP variations are dependent on both task demands and response characteristics for N1, N2, and P300 components.

Membrane cross-talk in the early distal tubule segment of frog kidney: role of calcium stores and chloride

The activities of transport mechanisms in epithelial cells are generally coordinated in order to minimise disturbances in cellular ion content and volume. Furosemide, a potent inhibitor of transport in the renal diluting segment, up-regulates apical K+ channel activity following the release of calcium from intracellular stores. The signal pathway between furosemide application and this calcium release is not known. Single early distal tubule segments from frog kidney were permeabilised with saponin in order to monitor calcium levels within cytoplasmic stores using the calcium-sensitive dye, mag-fura. The uptake (or release) of calcium to (or from) stores was initiated by adding agents to the bath solution, which is in direct contact with the intracellular organelles. ATP promoted calcium uptake into stores, whereas ATP removal led to a slower, spontaneous calcium release. Following loading, calcium stores could be rapidly depleted by inositol 1,4,5-trisphosphate (IP3), but not ryanodine. Calcium release was evident upon lowering the "intracellular" chloride concentration from 12 to 4 mM, equivalent to the fall in chloride induced by furosemide in intact cells. These results suggest that intracellular chloride may function as a second messenger, mediating cross-talk between the apical membrane and intracellular calcium stores.

Nursing Staff's Attitudes Toward Seclusion & Restraint

1. Staff preferred to treat patients as they themselves wanted to be treated. 2. More than one third of respondents did not view seclusion and restraint use as a time for a therapeutic intervention. 3. If staff are practicing from their belief patterns, they will choose interventions to avoid use of seclusion and restraint. 4. The majority of respondents preferred using medication to treat out-of-control behavior because they considered it less restrictive.

Novel mutations in the GALK1 gene in patients with galactokinase deficiency

Galactokinase deficiency is an inborn error of galactose metabolism whose major clinical manifestation is the development of cataracts during the first months of life. Only 20 mutations have been reported to date and understanding of the functionally important domains of the galactokinase protein is still limited. Here we report four novel mutations in GALK1 that were identified in two unrelated patients with galactokinase deficiency. Three of these were amino acid substitutions: 1569C-->T in exon 2 (R68C); 7093C-->T in exon 6 (T288M) and 7538G-->C in exon 8 (A384P). In addition, a single base-pair deletion was found in exon 5 (2833delC), predicted to result in a shift of the reading frame and a premature termination codon at position 263. Some differences with the GALK1 sequence deposited in Genbank are also reported.

Pain management program follow-ups. a national survey of current practice in the United Kingdom

In the United Kingdom (UK), the number of multidisciplinary pain management programs (PMP) has sharply increased in the last decade. Treatment aims to effect long-term changes, yet arrangements for evaluating long-term treatment outcome in routine practice remain unknown. All PMPs identified in the UK were invited to provide information by mailed questionnaire on aspects of follow-up evaluation. Sixty-six of 70 PMPs identified were successfully contacted (94% response rate). Ten of 48 PMPs (21%) provided complete data and met suggested criteria for adequate length and rates of follow-up, and outcome measurement. Levels of staffing and content explained only a proportion of the variability seen. A general commitment to follow-up outcome evaluation by PMPs was identified but there was substantial variability among programs in length of follow-up, attendance rates, and outcome measurement. These findings raise issues about the consistency of follow-up evaluation across the UK and the ability of current arrangements in some PMPs to accurately determine the longer-term outcome of chronic pain patients. Incorporating follow-ups into existing desirable criteria and agreeing on core outcome measures are two options available to service providers.

Structural ( n, m) determination of isolated single-wall carbon nanotubes by resonant Raman scattering

We show that the Raman scattering technique can give complete structural information for one-dimensional systems, such as carbon nanotubes. Resonant confocal micro-Raman spectroscopy of an (n,m) individual single-wall nanotube makes it possible to assign its chirality uniquely by measuring one radial breathing mode frequency omega(RBM) and using the theory of resonant transitions. A unique chirality assignment can be made for both metallic and semiconducting nanotubes of diameter d(t), using the parameters gamma(0) = 2.9 eV and omega(RBM) = 248/d(t). For example, the strong RBM intensity observed at 156 cm(-1) for 785 nm laser excitation is assigned to the (13,10) metallic chiral nanotube on a Si/SiO2 surface.